A liquid crystal panel included in a liquid crystal display device does not emit light. Therefore, a backlight unit is required as a separate lighting device. In general, backlight units are roughly classified into a direct type and an edge-light type according to their mechanisms. An example of the edge-light type is disclosed in Patent Document 1. Patent Document 1 discloses a configuration including a case, a light guide plate, alight source, and a holding member. The light guide plate having a rectangular overall shape is held inside the case. The light source is disposed opposite and close to a side surface of the light guide plate. The holding member is for positioning the light guide plate disposed inside the case. The light guide plate is held inside the case such that an end of the light guide plate is freely movable. According to Patent Document 1, with a cutout formed in the light guide plate at a proper position to reduce thermal expansion of the light guide plate toward the light source, a force of holding the light guide plate is maintained at a proper level and thus move of the light guide plate caused by thermal deformation is controlled.